Acquired brain injury refers to any type of brain injury that occurs after birth. That is, brain injury resulting from an event such as stroke, trauma, infection, disease or prolonged lack of oxygen. Persons affected by an acquired brain injury will often suffer from impaired vision, whereby typically the visual field of the person is significantly reduced. It is not uncommon for the person affected to lose sight or suffer from severe deterioration in typically one half of their normal visual field, while still retaining normal sight in the unimpaired portion.
Traditionally, the testing and diagnosis of the limitations of a person's visual field, is conducted either in a clinical confrontational manner or via the use of a visual field analyser. These tests effectively map out the patient's remaining visual field or sphere of vision, mapping where objects are visible and distinguished. Clinical confrontational testing involves a clinician quickly determining the patient's extent of vision loss by requesting that the patient fix their gaze on a central point whilst moving an object through their field of vision. This test may be undertaken with the use of a pen, or alternative object, and enables the clinician to study the appearance and movement of the patient's eyes. Visual field analysers also require a patient to fix their gaze at a central point while various lights or other visual stimuli are displayed. The patient then notes which stimuli are visible within their field of vision. With enough visual stimuli the patient's effective visual field can be mapped out accurately for diagnosis and rehabilitation purposes. Once the remaining visual field is determined and mapped out, a suitable rehabilitation program focussing on utilising the remaining vision can be devised.
The problem with a traditional visual analyser is that it has limited use for rehabilitation. Clinical confrontational testing is also limited in its rehabilitation capability and is used to monitor progress or recession not to administer therapeutic programs. Both these predominantly testing devices and methods offer little use in assisting the patient to utilise more effectively their remaining sight. This is as the patient's head is fixed in position and their gaze is fixed at a central point. By instructing the patient to move their head and eyes in order to view the stimuli, the patient can be taught to use their residual visual field more effectively.
Traditional methods of testing vision impairment and subsequent rehabilitation techniques are specific to the purpose of either analysing or rehabilitating the patient. In order to assess and map the patient's remaining field of vision, traditional vision analysing equipment requires an operator to fire the sequence of visual stimuli of varying intensity and record whether the patient has seen the stimuli. This effectively precludes the clinician or operator from observing the patient's eye behaviour and head movement during testing. The observation of movement is important in determining the extent of the patient's vision loss, as the patient may compensate and attempt to view the stimuli with their remaining vision. Also the vision analyser can only be used to map out the patient's visual field and in certain circumstances rehabilitate the patient's deteriorated vision, where they are able to distinguish between different stimuli. Traditional vision analysers are single stimuli devices and assessors using devices cannot detect differences in the client's attention to visual stimuli. Other problems arising from the use of traditional vision analysers are that patients are required to concentrate and focus on a central point for a lengthy period of time, causing fatigue and inaccuracy of results. The level of concentration and complexity of instructions required to complete the task, may also lead to a person who is suffering from other impairments, such as cognitive or language deficits, producing an inaccurate result.
The human eye has a tendency to focus on or move towards any new visual stimuli, making traditional visual analysers inaccurate in determining a visual field map. This phenomenon also makes progress analysis difficult to accomplish, as conditions cannot easily be replicated. Also standardised or repetitive tests can be inaccurate, as the patient may grow accustomed to the visual stimuli and move his/her eye accordingly.
It is therefore an object of the present invention to overcome or at least ameliorate one or more of the aforementioned problems or to provide the public with a useful alternative.